Condensed imidazopyridine derivatives of the present invention are compounds described in JP 1993/286973A and known to be useful as psychotropic agents, antianxiety agents, anesthesia antagonistic agents, and cerebral function activators. In the above publication, a method for producing the condensed imidazopyridine derivatives which are cyclized by using N-methyl-2-pyrrolidone, biphenyl ether-biphenyl mixture etc. is described. But it was very difficult to use this method for industrial production because it is necessary to react at 150° C. to 250° C.
This publication only describes that 2-(3-isoxazolyl)-3,6,7,9-tetrahydroimidazo[4,5-d]pyrano[4,3-b]pyridine or salts thereof were obtained just as white crystals and does not indicate preferable crystal forms of phosphate or phosphate monohydrate.
Abstract of the 23rd Congress of Heterocyclic Chemistry, pp.97–99, 1992 discloses a reaction for obtaining heterocyclic sulfonyl compounds from its chloro compounds by using a sulfinic acid salt as a catalyst and thus obtained sulfonyl compounds are easily reacted by nucleophilic substitution of carbanions. But the publication does not suggest an affection by addition of a catalyst such as an acid or a salt of an organic base, specifically methanesulfonic acid.